The Collaborative International Dictionary of English v.0.48:

Nervous \Nerv"ous\ (n[~e]rv"[u^]s), a. [L. nervosus sinewy,
   vigorous: cf. F. nerveux. See Nerve.]
   1. Possessing nerve; sinewy; strong; vigorous. "Nervous
      arms." --Pope.
      [1913 Webster]

   2. Possessing or manifesting vigor of mind; characterized by
      strength in sentiment or style; forcible; spirited; as, a
      nervous writer.
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   3. Of or pertaining to the nerves; seated in the nerves; as,
      nervous excitement; a nervous fever.
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   4. Having the nerves weak, diseased, or easily excited;
      subject to, or suffering from, undue excitement of the
      nerves; easily agitated or annoyed.
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            Poor, weak, nervous creatures.        --Cheyne.
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   5. Sensitive; excitable; timid.
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   6. Apprehensive; as, a child nervous about his mother's
      reaction to his bad report card.
      [PJC]

            Our aristocratic class does not firmly protest
            against the unfair treatment of Irish Catholics,
            because it is nervous about the land. --M. Arnold.
      [1913 Webster]

   Nervous fever (Med.), a low form of fever characterized by
      great disturbance of the nervous system, as evinced by
      delirium, or stupor, disordered sensibility, etc.

   Nervous system (Anat.), the specialized coordinating
      apparatus which endows animals with sensation and
      volition. In vertebrates it is often divided into three
      systems: the central, brain and spinal cord; the
      peripheral, cranial and spinal nerves; and the
      sympathetic. See Brain, Nerve, Spinal cord, under
      Spinal, and Sympathetic system, under Sympathetic,
      and Illust. in Appendix.

   Nervous temperament, a condition of body characterized by a
      general predominance of mental manifestations. --Mayne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nervous system
    n 1: the sensory and control apparatus consisting of a network
         of nerve cells [syn: nervous system, systema nervosum]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "nervous system":
   afferent neuron, autonomic nervous system, axon, brain,
   central nervous system, cerebral cortex,
   craniosacral nervous system, dendrite, effector organ,
   efferent neuron, ganglion, gray matter, internuncial neuron,
   medullary sheath, nerve, nerve trunk, neuron,
   peripheral nervous system, plexus, sensorium, sensory area,
   sensory cell, solar plexus, spinal cord, synapse,
   thoracolumbar nervous system, white matter